title: Identification of a novel chimeric gene, orf725, and its use in development of a molecular marker for distinguishing among three cytoplasm types in onion (Allium cepa L.).
abstract: A novel chimeric gene with a 5' end containing the nearly complete sequence of the coxI gene and a 3' end showing homology with chive orfA501 was isolated by genome walking from two cytoplasm types: CMS-S and CMS-T, both of which induce male-sterility in onion (Allium cepa L.). In addition, the normal active and variant inactive coxI genes were also isolated from onions containing the normal and CMS-S cytoplasms, respectively. The chimeric gene, designated as orf725, was nearly undetectable in normal cytoplasm, and the copy number of the normal coxI gene was significantly reduced in CMS-S cytoplasm. RT-PCR results showed that orf725 was not transcribed in normal cytoplasm. Meanwhile, the normal coxI gene, which is essential for normal mitochondrial function, was not expressed in CMS-S cytoplasm. However, both orf725 and coxI were transcribed in CMS-T cytoplasm. The expression of orf725, a putative male-sterility-inducing gene, was not affected by the presence of nuclear restorer-of-fertility gene(s) in male-fertility segregating populations originating from the cross between a male-sterile plant containing either CMS-T or CMS-S and a male-fertile plant whose genotypes of nuclear restorer gene(s) might be heterozygous. The specific stoichiometry of orf725 and coxI in the mtDNA of the three cytoplasm types was consistent among diverse germplasm. Therefore, a molecular marker based on the relative copy numbers of orf725 and coxI was designed for distinguishing among the three cytoplasm types by one simple PCR. The reliability and applicability of the molecular marker was shown by testing diverse onion germplasm.
authors.affiliation: Department of Plant Biotechnology, Biotechnology Research Institute, Chonnam National University, Gwangju, 500-757, South Korea. dronion@jnu.ac.kr
authors.forename: Sunggil
authors.initials: S
authors.lastname: Kim
authors.forename: Eul-Tai
authors.initials: ET
authors.lastname: Lee
authors.forename: Dong Youn
authors.initials: DY
authors.lastname: Cho
authors.forename: Taeho
authors.initials: T
authors.lastname: Han
authors.forename: Haejeen
authors.initials: H
authors.lastname: Bang
authors.forename: Bhimanagouda S
authors.initials: BS
authors.lastname: Patil
authors.forename: Yul Kyun
authors.initials: YK
authors.lastname: Ahn
authors.forename: Moo-Kyoung
authors.initials: MK
authors.lastname: Yoon
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003593:Cytoplasm / Q000235:genetics*; D004272:DNA, Mitochondrial; D003576:Electron Transport Complex IV / Q000235:genetics; D005298:Fertility / Q000235:genetics; D005819:Genetic Markers; D008969:Molecular Sequence Data; D050506:Mutant Chimeric Proteins / Q000235:genetics*; D019697:Onions / Q000235:genetics* / Q000648:ultrastructure; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics*; D011058:Pollen / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D004272:DNA, Mitochondrial; D005819:Genetic Markers; D050506:Mutant Chimeric Proteins; D010940:Plant Proteins; D003576:Electron Transport Complex IV